(LAY-zer): A device that concentrates light into an intense, narrow beam used to cut or destroy tissue. It is used in microsurgery, photodynamic therapy, and for a variety of diagnostic purposes.

: A rounded mass of lymphatic tissue that is surrounded by a capsule of connective tissue. Also known as a lymph gland. Lymph nodes are spread out along lymphatic vessels and contain many lymphocytes, which filter the lymphatic fluid (lymph).

(ma-LIG-nant): Cancerous; a growth with a tendency to invade and destroy nearby tissue and spread to other parts of the body.

(MEL-a-nin): The substance that gives the skin its color.

(mel-AN-o-sites): Cells in the skin that produce and contain the pigment called melanin.

: A form of skin cancer that arises in melanocytes, the cells that produce pigment. Melanoma usually begins in a mole.

(meh-TAS-ta-size): To spread from one part of the body to another. When cancer cells metastasize and form secondary tumors, the cells in the metastatic tumor are like those in the original (primary) tumor.

: Skin cancer that arises in basal cells or squamous cells but not in melanocytes (pigment-producing cells of the skin).